Fuzzy Adaptive Coordination of Virtual Inertia and Damping in a Wind–PV Sending-End MMC-HVDC System

Wind–photovoltaic (PV) modular-multilevel-converter-based high-voltage direct-current (MMC-HVDC) collection systems have limited inherent inertia and are vulnerable to frequency disturbances caused by renewable power fluctuations. Moreover, frequency deterioration and recovery impose different and partially conflicting requirements on virtual inertia and damping. To address this problem, an asymmetric Gaussian fuzzy coordination method is proposed for the virtual synchronous generator (VSG)-controlled sending-end MMC. A low-frequency model is first established to characterize the effects of wind–photovoltaic power variations on the collection-bus frequency. The frequency deviation and rate of change of frequency (RoCoF) are then used to identify the frequency-evolution state and generate coupled adjustments of virtual inertia and damping. Nonuniform and asymmetric Gaussian membership functions enhance sensitivity near the nominal operating point and distinguish the regulation requirements during deterioration and recovery. Simulations under three representative disturbance cases show that the proposed method reduces the maximum frequency deviation by 19.4–28.6% and shortens the recovery time by 17.5–24.4% compared with fixed-parameter control. The alternating-current voltage and current and direct-current-link voltage remain within acceptable ranges. Furthermore, 20 randomized tests demonstrate consistent frequency performance without current or voltage-limit violations.